1. Field of the Invention
The present invention relates to a back-illuminated type solid-state image pickup apparatus and a camera module.
2. Description of the Related Art
In recent years, video cameras and electronic cameras have been spread widely. A charge coupled device (CCD) solid-state image pickup element and an amplification type solid-state image pickup element (complementary metal oxide semiconductor (CMOS) image sensor) have been used for the cameras. Particularly, with the spread of portable electronic equipments including a camera module such as a notebook personal computer, there is an increased demand for reducing the size, the weight, the thickness, and the cost of the camera module.
In general, a solid-sate image pickup apparatus has a chip which is formed by arranging photoelectric conversion elements, an amplifying circuit, and a multilayered wiring layer formed with a microlens and a color filter thereon, on a silicon substrate. A cover glass is bonded on a first main surface (light-receiving surface) of the chip, interposing a spacer such as an adhesive therebetween. A terminal is provided on a second main surface side of the chip. A camera module has a configuration in which a lens, a filter, and the like are assembled, hardened by resin, and packaged, on the cover glass of the solid-state image pickup apparatus. The camera module is also mounted on a mounting substrate.
In a conventional solid-state image pickup apparatus, a photoelectric conversion element is formed on a substrate, and a multilayered wiring layer is formed thereon. However, in such a structure, light incident on the front surface side of the substrate is shielded by the multilayered wiring layer and the like. Accordingly, a sufficient focusing property cannot be obtained. Subsequently, in recent years, a back-illuminated type solid-state image pickup apparatus that allows light incident on the rear surface side of the substrate and carries out photoelectric conversion in the substrate has been produced (see for example, JP-A 2006-120805 (KOKAI)). The back-illuminated type solid-state image pickup apparatus includes a photoelectric conversion element that receives light entering from the rear surface (light-receiving surface) of a silicon substrate and performs photoelectric conversion, and various field-effect transistors that amplify and transfer signal charges accumulated in the photoelectric conversion element, and read out the signal charges, in a region on the front surface (surface opposite to the light-receiving surface) of the silicon substrate being isolated by an element isolation region. The back-illuminated type solid-state image pickup apparatus has a configuration in which a multilayered wiring layer is formed on the front surface of the silicon substrate where the photoelectric conversion element and the field-effect transistors are formed. In the disclosed conventional solid-state image pickup apparatus, to prevent the light entering from the side of the light-receiving surface from transmitting through the silicon substrate, being reflected on the multilayered wiring layer, and entering into the photoelectric conversion element, a transmission preventing film is provided at an interface between the silicon substrate and the multilayered wiring layer. The transmission preventing film prevents light entering from the side of the light-receiving surface and transmitted through the silicon substrate, from reaching to the wiring layer.
To meet the recent demand for reducing the size, the weight, and the thickness of electronic devices, for example, some electronic equipment such as a mobile phone is configured so that the solid-state image pickup apparatus and the camera module are mounted on a thin substrate, such as a flexible substrate. However, in the electronic equipment such as the mobile phone, many light generating sources such as a liquid crystal backlight and a button illumination light are used. Therefore, the light generated on the side surface and the rear surface of the solid-state image pickup apparatus and the camera module, mounted on the thin substrate such as the flexible substrate, sometimes enters into the photoelectric conversion element. As a result, there is a problem that the wirings at the front surface side (the side opposite to the light-receiving surface) are picked up by an image pickup element. Particularly, in the back-illuminated type solid-state image pickup apparatus, to incident light on the rear surface side, a silicon substrate is thinned approximately 5 to 10 micrometers, and at the front surface side (the side opposite to the light-receiving surface) thereof, those other than metal wirings are formed of an insulating material that transmits light. Accordingly, the light incident on the front surface side and the side surface side transmits through the multilayered wiring layer at the front surface side, and reaches the silicon substrate. Because light is not attenuated by the silicon substrate, the pickup of light other than the light from the subject has been a large issue.
In the conventional example, to prevent diffused reflection and the like from the rear surface (the side of the light-receiving surface), a transmission preventing film is provided on an interface between the silicon substrate and the multilayered wiring layer. The transmission preventing film prevents the light incident on the side of the light-receiving surface from transmitting through the side of the multilayered wiring layer. However, a configuration to prevent light incident on the surface opposite to the rear surface (front surface side, in other words, the side of multilayered wiring layer) has not been focused. Accordingly, in the configuration of the disclosed conventional solid-state image pickup apparatus in which the transmission preventing film is only formed at the photoelectric conversion element, the source/drain regions of and transistors, and the upper surface of the gate electrode, there is a problem that light incident from an oblique direction cannot be prevented from entering into the photoelectric conversion element, in the other regions where the transmission preventing film is not formed, for example, in the element isolation region.